Update python-tests.yaml

Author: saul-data

.github/workflows/python-tests.yaml

@@ -12,6 +12,10 @@ jobs:
     strategy:
       matrix:
         python-version: ["3.8", "3.9", "3.10"]
+        os:
+          - 'ubuntu-latest'
+          - 'macos-latest'
+          - 'windows-latest'
 
     steps:
       - uses: actions/checkout@v3